This invention relates to solutions capable of efficiently cleaning surfaces susceptible to biofilm coating thereon. It further relates to a cleaning/disinfecting solution, comprising the cleaning components and a bactericidal effective amount of a disinfectant.
Bacteria in natural aquatic environments have the marked tendency to interact with surfaces. The formation of surface biofilms can be regarded as a universal bacterial strategy for survival and for optimum positioning with regard to available nutrients. Bacteria growing in natural environments produce extensive exopolysaccharide (EPS) polymers that mediate both their attachment to surfaces and the formation of microcolonies and, eventually, the generation of biofilms. Biofilms are much more resistant to destruction than planktonic microorganisms. Although the mechanisms of this resistance are poorly understood, EPS are likely to play a role. In addition, biofilm bacteria are substantially resistant to surfactants, biocides and antibiotics. Two problems can arise from the presence of biofilms in a distributing aqueous system. First, the biofilm can clog pipes and tubings or interfere with the proper function of mechanical devices. Second, bacterial populations living in this protected mode of growth produce planktonic cells that contaminate fluids and alter their properties or, in the case of pathogens, can result in food poisoning or infections. It has also been proposed that biofilms could allow the multiplication of microbial pathogens stochasticly present in freshwater, as well as providing a mechanism for bioaccumulation of toxic substances. As a result, microbial biofilms constitute major industrial and medical concerns. These concerns are now being realized in the dental profession.
Dentists, dental surgeons and dental hygienists and their patients are well aware of the importance of meticulously sterilizing and disinfecting dental instruments. Indeed, since dental instruments are used directly in a patient""s mouth, sometimes for invasive or surgical procedures, it is of paramount importance to minimize the presence of microorganisms carried by dental instruments. The microorganisms can range from relatively harmless bacteria to dangerous pathogens. Consequently, efforts are deployed to remove microorganisms from dental instruments and from the fresh water lines feeding dental instruments such as air/water seringes, high speed turbines, and ultrasonic scalers, or from saliva evacuation lines. For most hand held dental instruments, thermal sterilization remains one of the best methods for eradicating microorganism. However, thermal sterilization is obviously not practical for the decontaminating of fresh water lines which remain to this date difficult to rid of microorganisms.
It is well known in the dental profession that small diameter pipes carrying fresh water are contaminated by bacteria and other microorganisms contained in the water flowing through them (Barbeau et al. 1996). Some of the microorganisms inevitably adhere to the inner walls of the lines and accumulate together with microscopic sediments or other substances into what is commonly known as a biofilm (Barbeau et al. 1997). The biofilm quickly and tenaciously coats the inner walls of the lines and becomes a reservoir for the proliferation of microorganisms. Bacterial populations will rapidly reach alarming levels which will also be found in the water discharge from the dental instruments connected to the fresh water line. For example, the average bacteria count in the water discharge of dental instruments is known to be of approximately 200,000 colony forming units per milliliter (cfu/ml) and in some extreme cases can reach 10,000,000 cfu/ml (Barbeau et al. 1996).
Jacquelin et al. (Path. Biol. 42(5): 425-431 (1994)) disclose compositions comprising a detergent such as sodium dodecyl sulfate (SDS) or sodium deoxycholate (SDC) and a phenolic disinfectant. The solutions are not efficient to remove and/or destroy biofilms as seen from the photographs of FIG. 1 and from the concluding remarks of this reference.
Whittaker et al. (Appl. and Env Microbiol. 43(3): 395-403 (1984)) disclose a plurality of compositions tested for their cleaning/disinfecting properties against micoorganisms. Their best composition was SDS/urea, which was efficient on chlorine-treated osmosis membranes after 11 days of treatment, which time is far from being a practical cleaning/disinfecting time for dentistry.
European patent publication 109 279 describes a solution comprising a plurality of essential ingredients for sterilizing surgical apparatuses. Although this reference suggests that biofilm decontamination is contemplated, there is no demonstration whatsoever on that specific issue. Moreover, there is no teaching of any subset of combined ingredients which would be capable by itself to remove the biofilm, and optionally, to kill the embedded bacteria.
A commercially available mouthwash sold under the trademark PLAX which comprises SDS 0.25%, sodium benzoate 2% and sodium salicylate 0.2%, supposedly helps in removing dental plaque prior to tooth brushing. The efficacy of this solution against biofilms in general is however doubtful given the short time of contact within which dental plaque is to be removed, even when tooth brushing follows.
Patent publication WO 96/20737, assigned to the present proprietor, describes compositions capable of cleaning and disinfecting biofilm-coated surfaces. These compositions comprise SDS 1%-2%, hydrogen peroxide 5%, EDTA 1%, mandelic and lactic acids in individual 1% concentration or in combined 2% concentration (mandelic acid being a bactericide). They further describe sub-compositions comprising the same concentrations of SDS/hydrogen peroxide/EDTA and SDS/acids. There is no teaching in these publications of compositions which would be different therefrom and still equivalent thereto, and there is no teaching of how specific components attack the integrity of the biofilms e.g. there is no mechanism of action proposed which would lead to establish a generic class of components useful for the purpose of removing biofilms with high efficacy.
Accordingly there still remains a need for compositions for cleaning biofilm-coated surfaces which will effectively dislodge a biofilm and optionally kill the microorganism flora in the dislodged biofilm, these compositions being adapted upon a variety of industrial uses and needs.
Against all expectations and documented evidence, the present inventors found that effective removal of biofilm may be achieved, using a solution minimally comprising a detergent and acids which, at the working pH, form salts in a substantial proportion. These two components by themselves are sufficient to remove well-established biofilms in a period of time varying from within 1 hour to an indefinite time, more preferably between about 1 hour and 18 hours.
When destruction of microorganisms is a concern, particularly in the medical or dental professions, a bactericide must be added to the solution. The bactericide contacts the surface rid of biofilm and wherein residual microorganisms retained on the surface will be killed. Preferably, the disinfecting and cleaning actions are allowed to occur concurrently.
In accordance with the present invention is provided a solution for dislodging a biofilm from a surface, which comprises an effective dislodging amount of a detergent and an effective dislodging amount of a salt or of an acid which forms a salt at a working pH value, or both, said salt being capable of displacing divalent cations present in the structure of the biofilm with the proviso that the composition is neither a mixture of SDS 1%-2% and EDTA 1%, a mixture of SDS 1%-2% and mandelic and lactic acids, each at an individual concentration of 1% or in a combined concentration of 2%, nor a mixture of SDS 0.25%, sodium salicylate 0.2% and sodium benzoate 2% (PLAX), all percentages representing final weight per volume concentrations.
The acid or salt is preferably an organic acid or salt. The components of the solution would preferably exclude components that comprise or produce an oxidant namely an oxygen-producing species such as peroxide or a chlorine-producing species such as sodium hypochlorite.
The components of the solution would preferably exclude a bactericide which is a terpene known from WO 93/17558.
Despite the fact that some components are excluded from the compositions of this invention, the use of all these compositions including the disclaimed ones for their capacity to remove biofilm is within the scope of the present invention.
It is another object of this invention to provide a composition for dislodging and destroying a biofilm, which further comprises a bactericide although it excludes the above-disclaimed bactericides.
In preferred embodiments, the detergent is SDS in a concentration excluding the above disclaimed species of at least about 0.1% or any detergent having a biofilm dislodging potency substantially equivalent thereto. The acid is mandelic acid in a concentration of at least about 0.1% at a working pH value (pH 5 is one example), or a mandelate salt, or any acid or salt having a biofilm dislodging potency substantially equivalent thereto at a suitable working pH. For example, the salt or acid may interestingly be an EDTA salt or acid in a concentration of at least about 0.25% at a working pH value. At pH 5, EDTA acid forms EDTA salt and is performing when combined to SDS, with or without any other acid, although better results were obtained with another acid.
In more preferred embodiments, the acid is selected from the group consisting of mandelic, 2-ketoglutaric, acetic, iminodiacetic, mucic, glycolic, fumaric, lactic, aspartic, phosphoric, pyruvic, chloroacetic, oxalic, citric, oxamic, malic, dichloroacetic, phenylacetic, benzylic, maleic, succinic, chloromandelic, glutamic, nitrilotriacetic, boric, adipic, formic, glucuronic, salicylic, benzoic, benzoyl formic, phthalic, ketopimelic acids, alanine, serine, tryptophan, tyrosine, bicine, tricine and glycine. Except for phosphoric acid, all these preferred acids are organic acids. When a bactericidal activity is needed, a bactericide such as hydrogen peroxide or any bactericide having a bactericidal potency substantially equivalent thereto may be added. Other bactericides like phenol derivatives or sodium hypochlorite are examples of good bactericides. They have been used in concentrations of at least 0.1% and 0.5%, respectively. In even more preferred embodiments, the composition further comprises biofilm dislodging enhancer agents such as chaotropic agents or calcium chelators.
A calcium chelator such as EDTA, preferably in a salt form, in a concentration of at least about 0.25% or any calcium chelator having a chelating potency substantially equivalent thereto may be added.
A chaotropic agent such as SDS in a concentration of at least about 0.1% or any chaotropic agent having a chaotropic potency substantially equivalent thereto may also be added.
In more preferred embodiments, the compositions comprise at least about 0.1% SDS, at least about 0.1% acid, at least about 0.25% EDTA, the acid being selected from the group consisting of 2-ketoglutaric, acetic, iminodiacetic, mucic, glycolic, fumaric, aspartic, phosphoric, pyruvic, chloroacetic acids and alanine.
In a mostly preferred embodiment, the compositions comprise at least about 0.1% but less than 1% SDS, about 0.1%-2% acid, and at least about 0.25% but less than 1% EDTA, the acid being mandelic acid or any other of 2-ketoglutaric, acetic, iminodiacetic, mucic, glycolic, fumaric, aspartic, phosphoric, pyruvic, chloroacetic acids and alanine.
The highest concentrations confer a strength to the composition such as it is effective within one hour. The lowest concentrations confer a good performance within 18 hours.
Good bactericides comprise hydrogen peroxide about 5%, or phenol derivatives at least about 0.1%, or sodium hypochlorite at least about 0.5% These bactericides are tuberculocides e.g. they are active against Mycobacterium spp. which are resistant to a large panel of bactericides.